That knob isn't require for it to function. As long as he screwed it in, it should be fine. My Asus motherboard came with a broken lock. It still worked fine. He just make have a DOA card, or a cheap power supply that can't supply enough juice. It doesn't matter if it's 700 watts, or not.

where did I say it was required for it to work, read my post carefully, "it may be hard to tell" if the card is seated properly is hardly "it won't work without it", they are suggestions to what might be the problem, of course it's not required for it to function, but it's a pretty good indicator that the card is locked into place and if he broke it off he doesn't know how the retention clip works so there may be other things he is doing wrong, maybe he's doing all of this on a carpet floor and not discharging his static electricity before touching his parts...? only he knows, also if he was using enough force to break it off he might have clipped a capacitor or something else on the motherboard as well, it just strikes me funny that he broke it off and now the video card he used to have in there (and I assume was working fine) isn't working as well, doesn't sound like the card to me, sounds like he might have broke something else on the mobo and didn't notice or the cards aren't seated properly, more likely the first option...

it would also be nice to know what the exact model of psu it was to try to eliminate another potential problem, though I have doubts that a 700w psu wouldn't power a 260 though, even if it was a garbage brand, the 260 would only pull 300w max and even if the psu was cheap it would probably put out at least 500w-600w with a full load and boot up is hardly full load...

where did I say it was required for it to work, read my post carefully, "it may be hard to tell" if the card is seated properly is hardly "it won't work without it", they are suggestions to what might be the problem, of course it's not required for it to function, but it's a pretty good indicator that the card is locked into place and if he broke it off he doesn't know how the retention clip works so there may be other things he is doing wrong, maybe he's doing all of this on a carpet floor and not discharging his static electricity before touching his parts...? only he knows, also if he was using enough force to break it off he might have clipped a capacitor or something else on the motherboard as well, it just strikes me funny that he broke it off and now the video card he used to have in there (and I assume was working fine) isn't working as well, doesn't sound like the card to me, sounds like he might have broke something else on the mobo and didn't notice or the cards aren't seated properly, more likely the first option...

it would also be nice to know what the exact model of psu it was to try to eliminate another potential problem, though I have doubts that a 700w psu wouldn't power a 260 though, even if it was a garbage brand, the 260 would only pull 300w max and even if the psu was cheap it would probably put out at least 500w-600w with a full load and boot up is hardly full load...

I'm agreeing with you, haha. I said he wouldn't know unless he's screwing the card in. Watts doesn't matter as much as amps do. If his card is supplying enough on the rails, it won't start.